The crawler-type travel devices generally include components such as a crawler belt, a sprocket wheel, an idler tumbler, and top and bottom rotational wheels. In the crawler-type travel devices, driving force is delivered to the crawler belt from a driving source (e.g., engine) through the sprocket wheel. The crawler belt is thus driven and a vehicle is accordingly allowed to move.
FIG. 4 illustrates an example of the crawler-type travel devices. A pair of the crawler-type travel devices 1 is mounted to the transverse lateral sides of a vehicle body (not illustrated in the figure), respectively. A vehicle, including the vehicle body and the crawler-type devices 1, is allowed to move in response to driving of a pair of crawler belts 2. More specifically, each of the crawler-type travel devices 1 includes a track frame 3, an idler tumbler 4, a sprocket wheel 5, plural bottom rotational wheels 6, plural top rotational wheels 10, and the crawler belt 2.
The track frame 3 is disposed on either of the transverse lateral sides (i.e., right side or left side) of the vehicle body. The track frame 3 is a component for attaching the idler tumbler 4, the bottom rotational wheels 6, and the top rotational wheels 10 thereto. The idler tumbler 4 is disposed away from the sprocket wheel 5 in a longitudinal direction (i.e., front-to-rear direction). The idler tumbler 4 is mounted to the track frame 3 in a rotatable state. The idler tumbler 4 is configured to be rotated in conjunction with driving of the crawler belt 2. The sprocket wheel 5 is driven and rotated by driving force delivered from a driving source (e.g., engine). The bottom rotational wheels 6 are disposed on the bottom part of the track frame 3 while being disposed between the sprocket wheel 5 and the idler tumbler 4 in the longitudinal direction. The bottom rotational wheels 6 are mounted to the track frame 3 while being rotatable and pivotable up and down. The bottom rotational wheels 6 are configured to be rotated in conjunction with driving of the crawler belt 2. The top rotational wheels 10 are disposed on the top part of the track frame 3 while being rotatable with respect to the track frame 3. The top rotational wheels 10 are configured to be rotated in conjunction with driving of the crawler belt 2.
Each of the crawler belts 2 is an endless loop belt wound around the sprocket wheel 5, the idler tumbler 4, the bottom rotational wheels 6, and the top rotational wheels 10. As illustrated in FIG. 5, the crawler belt 2 includes plural shoe plates 7, a first link section 8, and a second link section 9. The shoe plates 7 are coupled in an endless-looped shape by the first link section 8 and the second link section 9.
The first link section 8 is composed of plural first link members 11. Each of the first link members 11 is fixed to each of the shoe plates 7. The first link members 11 are coupled to each other in order to couple the shoe plates 7 to each other. The second link section 9 has the same structure as the first link section 8. The second link section 9 is composed of plural second link members 12. The second link section 9 is separated from the first link section 8 in a direction parallel to the axial direction of components such as the sprocket wheel 5 and the bottom rotational wheels 6 (hereinafter simply referred to as “axial direction”).
FIG.6a and 6b illustrate a plan view and a side view of the link members. Specifically, FIG.6a illustrates a plan view of the first link members 11 and the second link members 12, whereas FIG.6b illustrates a side view of the first link members 11. The surfaces of the first link members 11, illustrated in FIG.6a, are opposed to the surfaces thereof to be attached to the shoe plates 7. A part of the surfaces, hereinafter referred to as “rail surface R”, makes contact with the idler tumbler 4, the bottom rotational wheels 6, and the top rotational wheels 10. Each of the first link members 11 includes a first end portion 13, a second end portion 14, and an intermediate portion 15. The first end portion 13 is one end of the first link member 11, and includes a pin hole 16. The pin hole 16 passes through the first link member 11 in the axial direction. A coupler pin 17 (see FIG.5) described below is press-fitted into the pin hole 16. The second end portion 14 is the other end of the first link member 11, and includes a bushing hole 18. The bushing hole 18 passes through the first link member 11 in the axial direction. A bushing 19 (see FIG.5) described below is press-fitted into the bushing hole 18. The intermediate portion 15 is positioned between the first end portion 13 and the second end portion 14.
Thickness of the first end portion 13 in the axial direction (i.e., vertical direction of FIG.6a) is less than that of the intermediate portion 15 in the axial direction. In a plan view, an axially outer lateral surface (hereinafter referred to as “outer lateral surface”) 13a of the first end portion 13 and an outer lateral surface 15a of the intermediate portion 15 are included in roughly the same plane. On the other hand, an axially inner lateral surface (hereinafter referred to as “inner lateral surface”) 13b of the first end portion 13 is recessed from an inner lateral surface 15b of the intermediate portion 15 in an axial outward direction. Further, a stepped portion 15c is formed between the inner lateral surface 13b of the first end portion 13 and the inner lateral surface 15b of the intermediate portion 15.
In a plan view, an inner lateral surface 14b of the second end portion 14 and the inner lateral surface 15b of the intermediate portion 15 are included in roughly the same plane. On the other hand, an outer lateral surface 14a of the second end portion 14 is recessed from the outer lateral surface 15a of the intermediate portion 15 in an axial inward direction. Further, a stepped portion 15d is formed between the outer lateral surface 14a of the second end portion 14 and the outer lateral surface 15a of the intermediate portion 15.
The first link section 8 is formed by coupling the first link members 11 in such a way that the first end portion 13 of each of the first link members 11 is overlapped with and coupled to the second end portion 14 of one of two adjacent first link members 11.
The second link members 12 have basically the same structures as those of the first link members 11 excluding the second link members 12 are symmetrical to the first link members 11. As illustrated in FIG. 5, each of the second link members 12 includes a third end portion 23, a fourth end portion 24, and an intermediate portion 25. The third end portion 23 is one end of each of the second link members 12, and corresponds to the first end portion 13. The third end portion 23 includes a pin hole 16. The fourth end portion 24 is the other end of each of the second link members 12, and corresponds to the second end portion 14. The fourth end portion 24 includes a bushing hole 18. The intermediate portion 25 is positioned between the third end portion 23 and the fourth end portion 24.
With the structure illustrated in FIG. 5, coupling of the first link members 11, coupling of the second link members 12, and coupling between the first link members 11 and the second link members 12 are achieved. Specifically, the bushings 19 are inserted and fixed into the bushing holes 18 of the first link members 11 and the bushing holes 18 of the second link members 12 by means of press-fitting. Further, the coupler pins 17 are inserted into the bushings 19, respectively. One end of the coupler pin 17 is inserted and fixed into the pin hole 16 of the first end portion 13 positioned on the outside of the second end portion 14 by means of press-fitting. On the other hand, the other end of the coupler pin 17 is inserted and fixed into the pin hole 16 of the third end portion 23 positioned on the outside of the fourth end portion 24 by means of press-fitting. The first link members 11 are coupled to each other in a rotatable state with the foregoing coupling structure. This is true to the second link members 12.
Patent Document 1: Japan Laid-Open Patent Application Publication No. JP-A-2006-89023